The present invention relates to an electrolyte-activated alkaline battery, particularly for generating electric energy for the propulsion of underwater systems.
Known batteries of the above type substantially comprise an electrochemical cell; a reservoir containing an anhydrous alkaline compound dissolvable in sea water to form a liquid electrolyte; and a system for forming and circulating the liquid electrolyte between the reservoir and the electrochemical cell.
According to one known solution, described for example in European Patent EP-B-0 307 292, the electrolyte forming and circulating system comprises a sea water inlet conduit; a pump communicating at the intake side with the inlet conduit, and at the delivery side with the reservoir; a device for regulating the temperature of the electrolyte supplied to the electrochemical cell; and a centrifugal gas separator connected to the outlet of the electrochemical call, and presenting a liquid phase outlet and a gaseous phase outlet. The gaseous phase outlet communicates with the outside environment via an exhaust conduit with a nonreturn valve for preventing inflow of sea water; and the liquid phase outlet is connected to the inlet conduit, and hence to the intake side of the pump, via an closure valve which is closed during certain operating stages of the battery in which the system operates in open-loop mode and sea water is drawn in from the outside, and is open during normal operation in which the system defines a closed-loop circuit for circulating the electrolyte between the reservoir and the electrochemical cell.
More specifically, the closure valve is closed during initial activation of the battery--in which the pump draws sea water into the reservoir to dissolve the anhydrous alkaline compound and form the liquid electrolyte--and during drainage and deactivation of the battery--in which respectively part or all of the electrolyte is drained off and replaced with sea water.
Batteries of the above type present a major drawback.
When draining and deactivating the battery, the liquid phase outlet is closed so that the liquid is forced out along the gaseous phase exhaust conduit, thus resulting in highly irregular two-phase flow and a sharp deceleration in outflow of the electrolyte.
Following drainage of the battery, a relatively long time is required for normal operating conditions, and particularly steady-state centrifugation of the liquid, to be restored.
Finally, the reduction in outflow speed of the electrolyte is even more critical in emergency situations in which the battery must be deactivated rapidly to avoid the risk of explosion.